Audio communication takes a large portion of human interaction. We conduct telephone conversations, listen to music or sound associated with TV shows and receive alert such as alarm clock or finish of a microwave oven or dishwasher cycle.
The natural wave behavior of acoustic signals and the relatively long wavelength results with large spreading of the sound waves and allows people located in a common region to hear the sound and perceive the data carried thereon.
Various techniques are known for allowing a user to communication via sound while maintaining privacy of the communication. Between such techniques, best known examples include the telephone receiver and headphones or earphones, all providing relatively low amplitude acoustic signals directed at one or both of the user's ears.
Binaural hearing ability of humans and animals enables them to locate sounds in three dimensions within an auditory space (i.e. to resolve direction and possibly also distance and distinguish between sounds arriving from different locations in the auditory space).
This is possible because the brain infers the direction and possibly also the distance/location of the sound source by comparing the binaural sounds sensed by the left and right ears to identify sound modifications/differences (sound cues) between the two ears that are indicative of the direction/location of the sound source. Among the sound cues included are time difference of arrival, and intensity difference due to a difference in the acoustical paths of propagation of the sound from the source to the two ears respectively, as well as spectral (frequency spectrum) modifications caused by interaction of the sounds arriving from the sound source with the head/ears anatomy, in which the original source sound is modified before it enters the ear canal for processing by the auditory system. The brain processes these modifications of the sounds captured by the two different ears to infer the direction and possibly distance of the sound source(s).
An illusion of three dimensional (3D) auditory space, a so-called virtual auditory space (VAS), can be generated by headphones by utilizing appropriate filtering of sounds presented over the headphones. When utilizing headphones, a head-related transfer function (HRTF) is typically used for carrying out appropriate filtering of the sounds presented over each individual one of the headphones for creating the VAS.
Generally the head-related transfer function (HRTF) is a response function characterizing how an ear of a user receives sound from a point in space. As indicated above, properties of the user's head and ears (e.g. size and shape and/or mechanical properties thereof), transform the sound sensed by the eardrum and thereby affect how sounds from different points in space are perceived, and particularly introduce different spectral modifications to sounds arriving to the user from different directions relative to the user. Typically, some sound frequencies (e.g. from 2-5 kHz) are amplified, while others are attenuated, while the parameters of the of the amplification/attenuation generally depend on the direction and possibly also distance of the sound source. Also as indicated above, time delay and intensity difference are introduced to sounds arriving from the same source to the left and right ears of the user, due to a difference in the acoustical path from the source to the two ears respectively.
A virtual auditory space (VAS) sensation can be created, for example by headphones by utilizing a couple of HRTFs for two ears of the user respectively, to synthesize binaural sound that is perceived by the user as coming from a particular direction/location in space. The HRTFs introduce spectral modifications to the sounds depending on the relative directions from which they arrive to the respective ears. The HRTF presents the spectral modifications applied by the head to sound propagating from a certain direction in free air until the sound arrives and is sensed by the eardrum of a particular ear. Moreover, typically proper relative time delays and intensity differences are also respectively introduced to the sounds transmitted to the two ears whereby the magnitude of the time delay and intensity difference depends on the different trajectories/paths (direct or indirect) of sounds from the particular direction/location of a sound source towards the respective ears.
Recently, novel techniques for producing/generating private/confined sound fields from a remote speaker (i.e. ultrasound traducer(s)) have been developed by the assignee of the present patent application. According to these techniques, a private/confined audible sound field (also often referred to as a “sound bubble”) can be generated at a certain location in space, while the sound generator transducer is remotely located.
More specifically, WO 2014/076707 discloses a system and method for generating a localized audible sound field at a designated spatial location. According to this technique, spatially confined audible sound carrying predetermined sound-data is produced locally at a designated spatial location at which it should be heard. Even more specifically, according to the disclosed technique in order to generate the locally confined audible sound carrying the desired sound-data, frequency content of at least two ultrasound beams are determined based on the sound data and the of at least two ultrasound beams are transmitted by an acoustic transducer system (e.g. transducer system including an arrangement of a plurality of ultrasound transducer elements) Then, the spatially confined audible sound is produced at the designated location by the at least two ultrasound beams. For example, the at least two ultrasound beams include at least one primary audio modulated ultrasound beam, whose frequency contents includes at least two ultrasonic frequency components selected to produce the audible sound after undergoing non-linear interaction in a non linear medium, and one or more additional ultrasound beams each including one or more ultrasonic frequency components. Location-data indicative of the designated location is utilized for determining at least two focal points for the at least two ultrasound beams respectively such that focusing the at least two ultrasound beams on the at least two focal points enables generation of a localized sound field with the audible sound in the vicinity of the designated spatial location.
WO 2014/147625, which is also assigned to the assignee of the present application, describes a transducer system including a panel having one or more piezo-electric enabled foils/sheets/layers and an arrangement of electric contacts coupled to the panel. The electric contacts are configured to define a plurality of transducers in the panel. Each transducer is associated with a respective region of the panel and with at least two electric contacts that are coupled to at least two zones at that respective region of the panel. The electric contacts are adapted to provide electric field in these at least two zones to cause different degrees of piezo-electric material deformation in these at least two zones and to thereby deform the respective region of the panel in a direction substantially perpendicular to a surface of the panel, and to thereby enable efficient conversion of electrical signals to mechanical vibrations (acoustic waves) and/or vice versa. The transducer of this invention may be configured and operable for producing at least two ultrasound beams usable for generating the spatially confined audible sound disclosed in WO 2014/076707 discussed above.